Hypertension is a serious health problem among blacks. Stroke mortality rates among U.S. blacks are twice the rates among whites. With the exception of a relationship with obesity among black women, little is known about the causes of excess risk for hypertension among blacks. Hypertension and related risk factors are in a relatively steady state among U.S. blacks and it is difficult to further delineate roles of various risk factors. In contrast, in the Nigerian population, many factors have been changing as development takes place and persons move from village to town to urban areas, frequently experiencing large changes in socioeconomic status and other environmental factors in the process. We studied 559 urban civil servants and found that prevalence of hypertension among the male professionals and administrators was 53% compared with 22% among non- professionals. Professional status, age, obesity and alcohol consumption were all independent predictors of blood pressure. We hypothesize that the differences in hypertension prevalence are primarily related to differences in socioeconomic status and will test the following hypotheses. The higher prevalence of hypertension among the higher SES professional subjects is related to higher weight, caloric intake, Westernization of diet, alcohol intake, Na intake, cardiovascular reactivity, and stress due to job, migration and change in SES, and to reduced K intake and physical exercise, and that insulin activity, waist-hip ratio, and left ventricular hypertrophy, possible markers of increased risk of hypertension, are higher in senior than in junior staff, even in the absence of hypertension. We will study 750 male and female civil servants systematically sampled from civil service employee lists. We will measure blood pressure (on three days), urinary Na and K (two overnight), dietary intake (two 24-hour recalls), physical measurements, electrocardiogram, urinary protein, serum insulin, stress in the work environment, migration history and cardiovascular reactivity (mirror tracing, speech presentation, hand ergonometer). Among U.S. blacks, approximately 80-90% of genes are from African ancestry. The current Nigerian population is one of the most closely related to the ancestral origins of U.S. blacks. Our findings in this population should contribute to our understanding of the etiology of hypertension among U.S. blacks.